【作者】 李学锋；

【导师】 官文超；

【作者基本信息】 华中科技大学 ， 材料物理与化学， 2005， 博士

【摘要】 碳纳米管（CNTs）自问世以来,以其独特的物理结构,优异的机械力学性能和广阔的应用前景受到人们的广泛关注,但因为它不溶解不熔融而不易加工,同时作为一种纳米材料极易发生团聚,使其进一步开发与应用受到很大的限制。从结构上来看,由sp²碳原子组成的CNTs 可以被视为线性富勒烯分子,每个碳原子的一个垂直于骨架平面的p 轨道形成高度离域化的大π键,能与含有π电子的化合物通过π-π非共价键作用相结合,得到化学修饰的CNTs。本文采用分子设计的方法,利用大分子的官能团反应制备聚乙二醇/碳纳米管（PEG/CNTs）和光敏性环氧丙烯酸酯/碳纳米管（EA/CNTs）;通过紫外光和热引发自由基聚合制备聚丙烯酰胺/碳纳米管（PAM/CNTs）,聚乙烯醇/碳纳米管（PVA/CNTs）,聚苯乙烯/碳纳米管（PSt/CNTs）,反式聚异戊二烯/碳纳米管（TPI/CNTs）和丙烯腈-丁二烯-苯乙烯/碳纳米管（ABS/CNTs）,七种CNTs 高分子衍生物。采用红外光谱（FTIR）、紫外-可见光光谱（UV-vis）和荧光发射光谱（Fluorescence）等对CNTs 高分子衍生物进行了结构表征,证明利用高分子反应方法可以实现对CNTs 的高分子修饰;透射电子显微镜（TEM）分析了CNTs 高分子衍生物在溶液中的形貌,除乳液聚合制备的PSt/CNTs 的微观形貌为小于100nm 的微球连接数百纳米长的微管,其它CNTs 高分子衍生物均为聚合物包裹在CNTs 外部,在管端头有较多聚合物聚集。PEG/CNTs、PAM/CNTs、PVA/CNTs 及PSt/CNTs 四种CNTs 高分子衍生物可方便的分散于水中,这一方面得到了可溶性CNTs,为化学工作者进一步深入研究CNTs 打开方便之门,另一方面可得到具有特定功能的CNTs 高分子衍生物,使其成为名副其实的最有前途的材料。采用四球摩擦试验机分别对PEG/CNTs、PAM/CNTs、PVA/CNTs 水溶液和PSt/CNTs 乳液及水溶性减磨剂壬基酚聚氧乙烯醚磷酸锌（OPZ）与CNTs 高分子衍生物的复合液,用作水基润滑液的摩擦学行为进行了研究。PEG/CNTs 和PAM/CNTs 的添加量分别在0.5%和0.3%时,对应最小磨斑直径D₃₀²⁰⁰为0.68mm 和0.62mm;PVA/CNTs 水溶液和PSt/CNTs 乳液与OPZ 润滑添加剂复配后,两种添加剂的添加量分别在0.25%和1.0%时,对应最小磨斑直径D₃₀⁴⁰⁰为0.38mm 和0.36mm,最大极压值分别为610N 和680N,显示了较好的减磨效果和润滑性能;润滑液的极压性能与CNTs 高分子衍生物的添加量有直接关系,浓度过大时,更多还原

【Abstract】 Carbon nanotubes (CNTs) have been one of the hottest research topics since the discovery because of their unique architecture, mechanical properties and wide potential applications. However, the CNTs have very high thermo stability and until now it cannot dissolve in any solvent, which limits the further development and application of CNTs remarkably. The CNTs is made of sp~2 carbon atoms, each of them contributes a p-electron to construct a highly delocalized πelectron cloud along the wall, which can combine with other molecules containing πelectrons through π-πinteraction, and get chemically modified CNTs. In this paper, seven CNTs derivatives were prepared including poly(ethylene glycol)/carbon nanotubes (PEG/CNTs) and epoxy acrylate/carbon nanotubes (EA/CNTs) by means of polymer groups reaction, polyacrylamide/carbon nanotubes (PAM/CNTs) derivative by an in-situ ultraviolet (UV) radiation initiated polymerization, acrylonitrile–butadiene–styrene/carbon nanotubes (ABS/CNTs) and trans-polyisoprene/carbon nanotubes (TPI/CNTs) by an UV radiation grafted reaction, poly(vinyl alcohol)/carbon nanotubes (PVA/CNTs) and polystyrene/carbon nanotubes (PSt/CNTs) by in-situ free radical polymerization. The microcosmic structures and morphology of the derivatives were characterized by the instruments of Fourier transform infrared spectroscopy (FTIR), UV-visible absorbance spectra (UV-vis), Fluorescence spectra (FS) and Transmission electron microscope (TEM). The results show that CNTs can be modified by polymer in-situ polymerization. And TEM shows that the PSt/CNTs colloid is tubes with tiny balls in nanometer scale, but in the images of other derivatives of CNTs, polymer is coated on the surface of CNTs and much more chains are assembled at the ends of CNTs. PEG/CNTs, PAM/CNTs, PVA/CNTs and colloidal PSt/CNTs that were synthesized can be resolved in water, which can open a convenient door for other chemists in further research. At same time special functional materials with CNTs can be made by this way, which makes CNTs becoming the most promising materials be worthy of the name. The tribology of behavior of CNTs derivatives and their complexes with OPZ (a type of water-soluble zinc alkoxyphosphate) as lubricant additives of water base stock was studied by four-ball tribotester. When the PEG/CNTs and PAM/CNTs content reach 0.5 wt.% and 0.3 wt.% respectively, the wear scar diameter (WSD) is minimum to 0.68 mm and 0.62 mm. When the PVA/CNTs and colloidal PSt/CNTs content reach 0.25 wt.% and 1.0 wt.% complexes with OPZ respectively, the WSD are minimum to 0.38 mm and 0.36 mm, and the maximum non-seized load (PB) are maximum to 610 N and 680 N. This infers that derivatives of CNTs have pretty good load carrying and anti-wear performance in water fluid. Their properties of lubrication are not proportional to its content, and excessive adding may lead descending of the lubrication properties. The worn surface in four-ball machine testing was observed by scanning electron microscope (SEM). The images demonstrated that the wear scar obviously became smaller and relatively smoother when adding the derivatives of CNTs as additive, which intuitionistically showed us their good lubrication properties. The friction signals of PEG/CNTs, PAM/CNTs and PVA/CNTs spin casting thin films could be measured at different applied loads for the same area in the friction force microcopy (FFM) map. Three derivatives have same characterization: derivative and homopolymer films exhibit stable and lower friction signals below the 100 nN load due to polymer soft chains and flat surface. However, after load of 100～140 nN, the difference in friction signals between the two films is larger. The friction coefficient decreased significantly as the CNTs addition. The results can be attributed to the additional load-bearing ability afforded by CNTs chemically bonded on the derivative chains which molecules are reasonable to consider anti-wear for its flexibilities. Based on the experimental study on water-soluble core-and-shell derivatives including CNTs additives made by our group, its lubrication mechanism was speculated preliminarily. It is supposed that derivative can penetrate into the interface and deposit there to support and isolate two relative motion surfaces during friction process, and has the possibility to cause microcosmic rolling effect between two rubbing surface. And therefore, the anti-wear performance of the base stock was improved. Further more, there are rolling effect with boundary lubrication in the complexes with the OPZ solution. UV curing coating of EA/CNTs was prepared by the molecule group reaction of CNTs with EA. The anti-infrared/ultraviolet property was characterized by UV-vis and FTIR preliminarily. The results demonstrated that, its transmittance was greater than 85%in visible spectrum, the transmittance was 42.3% in near infrared wave range (4000cm-1～14000 cm-1) and it shielded most of wave in ultraviolet region (< 300 nm). At same time the mechanical property of composite coating was improved. So this new nano-composite materials would be expected to be an anti-infrared/ultraviolet thin coating in functional applications. TPI/CNTs and ABS/CNTs composites were prepared by UV irradiated at room temperature. The resistivity of composites decreases 107 times with adding 5 wt.% CNTs. In the 20～100℃temperature range, the resistivity of UV irradiated composites almost keeps stability. In the 2～10GHz microwave range, the ε′′of composites are from 21 to 50. So the new composites would be potential electromagnetic shielding materials. In conclusion, the study on CNTs as functional materials is in the ascendant. Our works are based on the polymer chemically-modified CNTs, and to evaluate the tribology, optical, electrical and magnetism properties of polymer/CNTs, which will provide new ideologies and methods for tribology of CNTs.更多还原